The RAW files like Tiff are uncompressed ( unlike jpeg).
Raw however is largely unprocessed by the cameras internal digital processing software and as such gives you far more lassitude to adjust white balance, colour temperature and other exposure parameters more accurately than you can do on a tiff within a "normal " photo editing program .
Raw files are like digital negatives and the processing on them is always reversible as unlike Tiff ( and jpeg) where once saved that processing is permanent
As such Raw files need to be processed before becoming Tiff which can then be edited in Photoshop and the like
Unfortunately Raw file processing is not supported by all software for all cameras
So Jpegs are like compressed Tiffs
Tiffs are processed Raw files
Im aware that TIffs do get compressed but the illustrations were meant to be explanatory in as simple a way as possible:
"Lossless" compression is indeed compression but nothing as destructive as the lossy compression applied to jpegs
As such, the file sizes of RAW and TIff tend to be more similar than those of Tiffs and less compressed Jpegs
In film terms, a raw file is a negative. A Jpeg or a tiff file is a print - adjustments can be made to 'prints' but the process is destructive and limited, so most serious photographers prefer to work on the 'negatives'.
Raw files are proprietory file formats, i.e. they are designed and owned by their manufacturers and so it isn't safe to assume that all software programmes can be used with them, or that all can get the best from them. Photoshop CS2 is pretty good, and the now discontinued Rawshooter programmes were excellent, although neither supports all raw formats. Camera manufacturers always supply their own raw file coversion software.
Basically raw files are 'as captured' and the photographer is left to carry out all adjustments, for example colour balance, contrast, exposure, shadow/highlight detail and so on. Once the adjustments have been made you simply save a copy, in jpeg, tiff or psd format usually, leaving the original raw file untouched. You can go back to the raw file later if you wish.
You can also save two different versions - for example one with the exposure adjusted to suit shadow detail and one with it adjusted to suit highlight detail, and then combine the two images later.
Let me know if you'd like more specialised info on this.